Herbicidal thioparaconic acid derivatives

ABSTRACT

A method of controlling plant growth is provided comprising applying to the plants or to a habitat thereof a herbicidally effective amount of a compound having the structure: ##STR1## wherein R 1  is selected from the group consisting of carboxy, cyano, ester ##STR2##  or amido ##STR3##  wherein R 2  is selected from the group consisting of a straight-chained alkyl group or a branched-chain alkyl group, of about 1 to 8 carbon atoms, 
     R 3  and R 4  are selected from the group consisting of hydrogen, alkyl of about 1 to 8 carbon atoms, cycloalkyl of about 5 to 6 carbon atoms, and heterocyclyl of about 5 to 6 carbon and hetero atoms, or, 
     R 3  and R 4  taken together with the nitrogen atoms to which they are attached form a heterocyclyl group having 5 to 6 carbon and hetero atoms. Also, novel compounds having the above structure are provided.

FIELD OF THE INVENTION

The present invention relates to herbicides.

BACKGROUND OF THE INVENTION

In the food agricultural industry, it is useful to provide the publicwith a variety of herbicides. The herbicides of this invention arederivatives of thioparaconic acid.

U.S. Pat. No. 2,976,216, filed on Nov. 4, 1959, entitled "PermanentWaving Agent", assigned to The Gillette Company, Boston, Mass.,discloses a dry solid composition soluble in an aqueous medium to form ahair waving lotion comprising one molecular proportion of a member ofthe class consisting of thioparaconic acid and certain salts ofthioparaconic acid.

Fungicidally active thiolane-2,4-dione-3-carboxamides are disclosed inU.S. Pat. No. 4,599,350, issued on July 8, 1986, entitled "NovelThiolane-2,4-dione-3-carboxamide Fungicides", assigned to BayerAktiengesellschaft, Leverkusen, Fed. Rep. of Germany.

U.S. Pat. No. 3,365,447, issued on Jan. 23, 1968, entitled"2,5-Dihydro-4-hydroxy-2-oxothiophens", assigned to Imperial ChemicalIndustries Limited, London, England discloses thiophen derivatives whichpossess useful therapeutic properties.

Chemical Abstracts, 35: 2114(1940) refers to Arkiv Kemi, Mineral Geol.,14A: 22(1941) by B. Holmberg and E. Schjanberg wherein thioparaconicacid is disclosed.

Chemical Abstracts, 73: 3433^(m) (1970) refers to Mem. Fac. Eng., KobeUniv., 197: 151(1970) by H. Akashi, R. Masuda, C. Katsuda and T.Kobayashi, wherein the reaction scheme between itaconic acid andthiourea shows the structure of thioparaconic acid as an end product.

SUMMARY OF THE INVENTION

We have developed a method of controlling plant growth which provides analternative to existing methods.

More specifically, in accordance with the present invention, there isprovided a compound having the structure: ##STR4## wherein R¹ isselected from the group consisting of cyano, ester ##STR5## or amido##STR6## wherein R² is selected from the group consisting of astraight-chained alkyl group or a branched-chained alkyl group, of about1 to 8 carbon atoms,

R³ and R⁴ are selected from the group consisting of hydrogen, alkyl ofabout 1 to 8 carbon atoms, cycloalkyl of about 5 to 6 carbon atoms, andheterocyclyl of about 5 to 6 carbon and hetero atoms, or,

R³ and R⁴ taken together with the nitrogen atoms to which they areattached form a heterocyclyl group having 5 to 6 carbon and heteroatoms.

In accordance with another aspect of the invention, there is provided amethod of controlling plant growth comprising applying to the plants orto a habitat thereof a herbicidally effective amount of a compoundhaving the structure: ##STR7## wherein R¹ is selected from the groupconsisting of carboxy, cyano, ester ##STR8## or amido ##STR9## whereinR² is selected from the group consisting of a straight-chained alkylgroup or a branched-chained alkyl group, of about 1 to 8 carbon atoms,

R³ and R⁴ are selected from the group consisting of hydrogen, alkyl ofabout 1 to 8 carbon atoms, cycloalkyl of about 5 to 6 carbon atoms, andheterocyclyl of about 5 to 6 carbon and hetero atoms, or,

R³ and R⁴ taken together with the nitrogen atoms to which they areattached form a heterocyclyl group having 5 to 6 carbon and heteroatoms.

It is an advantageous feature of the invention that it providesherbicidal methods which are alternatives to existing herbicidalmethods.

It is also an advantageous feature of the invention that it providesnovel compounds useful in herbicidal methods.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides a compound having the structure: ##STR10##wherein R¹ is selected from the group consisting of cyano, ester##STR11## or amido ##STR12## wherein R² is selected from the groupconsisting of a straight-chained alkyl group or a branched-chained alkylgroup, of about 1 to 8 carbon atoms, such as methyl, ethyl, propyl,butyl, pentyl, octyl, isopropyl, i-butyl, s-butyl, t-butyl, 2-ethylhexyland isooctyl.

R³ and R⁴ are selected from the group consisting of hydrogen, alkyl ofabout 1 to 8 carbon atoms, such as the examples provided hereinabove,cycloalkyl of about 5 to 6 carbon atoms, such as cyclopentyl andcyclohexyl, and heterocyclyl of about 5 to 6 carbon and hetero atoms,such as furyl, thienyl, thiazolyl, oxazolyl, pyrazolyl, pyranyl,thiopyranyl, dioxanyl or,

R³ and R⁴ taken together with the nitrogen atom to which they areattached form a heterocyclyl group having 5 to 6 carbon and heteroatoms, such as pyrrolidinyl, piperidinyl and piperazinyl.

Preferred compounds of the invention include esters having the abovestructure wherein R² is selected from the group consisting of ethyl andpentyl.

Other compounds representative of the invention include amido compoundshaving the above formula wherein R³ and R⁴ are selected from the groupconsisting of hydrogen, methyl, ethyl, propyl and butyl.

Preferred amido compounds having the above formula include those whereinR³ and R⁴ are hydrogen or methyl.

The invention also provides a method of controlling plant growthcomprising applying to the plants or to a habitat thereof a herbicidallyeffective amount of a compound having the above structure wherein:

R¹ is selected from the group consisting of carboxy, cyano, ester##STR13## or amido ##STR14## wherein R², R³ and R⁴ are as defined above.

Preferred methods of the invention include those utilizing esters havingthe above formula wherein R² is selected from the group consisting ofethyl and pentyl.

Other methods representative of the invention include those utilizingamido compounds having the above formula wherein R³ and R⁴ are selectedfrom the group consisting of hydrogen, methyl, ethyl, propyl and butyl.

Other preferred methods of the invention include those utilizing amidocompounds having the above formula wherein R³ and R⁴ are hydrogen ormethyl.

In general, compounds of the invention wherein R¹ is ester or amido asdefined above are prepared according to the following reaction schemes:##STR15##

The esterification of acids with alcohols as shown above is generallydescribed in Advanced Organic Chemistry, 3rd Ed., by Jerry March (1985),page 348. The acylation shown above is also generally described inAdvanced Organic Chemistry, id at page 370. The carboxylic acid is knownand can be prepared as described in Chemical Abstracts 73: 3433^(m)(1970) discussed herein.

The preparation of compounds of the invention wherein R¹ is cyano asdefined above are generally prepared according to the following reactionscheme: ##STR16## This reaction scheme is generally disclosed also inAdvanced Organic Chemistry, id at page 933.

The cyano compound of the invention is preferably prepared according tothe following reaction scheme: ##STR17##

Application of the compounds which are useful in the process of theinvention for purposes of herbicidal control can be accomplishedemploying both conventional type formulation and equipment. Thecompounds may, for instance, be formulated as wettable powders, dusts,dust concentrates, emulsifiable concentrates and the like which areamenable to application with conventional spraying or dusting apparatus.

For use in agriculture, the herbicides useful in this invention may beadvantageously formulated as a wettable powder. Wettable powders areusually prepared by grinding and milling the ingredient with a solidcarrier, such as attaclay (attapulgite) kaolin, diatomaceous earth,synthetic calcium silicate, fullers earth(calcium montmorillonite),talc, pumice, and the like. Usually, about 25% to 75% by weight of solidcarrier, is used. In addition, there is generally added about 1% to 5%by weight of a dispersing agent, such as alkali metal salts ofnaphthalene sulfonic acid and anionic-nonionic blends, and from about 1%to 5% by weight of a surfactant, such as polyoxyethylene alcohols,acids, adducts, sorbitan fatty acid esters, sorbital esters, and thelike. The amount of solid carrier is then reduced accordingly tocompensate for the amount of dispersing agent(s) and surfactant(s)incorporated into the formulation.

Wettable powders are prepared in the same manner as the dustconcentrates excepting that about 1% to 5% by weight of a dispersingagent such as the calcium salt of a polymerized alkyl aryl sulfonicacid, sodium lignosulfate, or sodium salt of condensed naphthalenesulfonic acid is blended with the mixture and about 1% to 5% of asurfactant, such as polyoxyethylated vegetable oil, alkyl phenoxypolyoxyethylene ethanol, sodium alkyl naphthalene sulfonate is alsoblended with the formulation.

Wettable powder formulations are generally prepared by admixing fromabout 25 percent to about 95 percent, by weight, of active ingredientwith finely ground clay, such as kaolin or attapulgite, either with orwithout a surface active agent, emulsifier or spreader-sticker. Thelatter is then dispersed in water for spray application.

Wettable powders are usually dispersed in water and applied as diluteaqueous sprays at a rate of 0.28 kg to 22.4 kg/hectare of activeingredient to the area where control of undesirable plant species isdesired.

In practice, the wettable powder is dispersed in water and applied as aliquid spray to the foliage of undesirable plants. Application ratesshould be sufficient to provide about 0.25 to 10 pounds per acre of thepyrazolium salt and, although 0.5 to 5.0 pounds per acre of said salt isgenerally satisfactory to control undesirable broadleaf weeds andundesirable grass plants, it should be recognized that rates exceeding10 and as high as 20 pounds per acre can be used. These higher rateswould, of course, be used in areas such as railroad sidings, beneathpower lines and along hedge rows bordering property lines and fields.

Advantageously, many of the compounds useful in the process of thisinvention demonstrate a high degree of water solubility and lendthemselves to the preparation of aqueous concentrates. Among thepreferred salts are the alkali metal, ammonium or alkylammonium ones. Inpractice, the aqueous concentrates may be applied directly as a liquidspray to the foliage of undesirable broadleaf weeds and grassy plants.Alternatively, they may be further diluted with water and applied asdilute aqueous sprays to these undesirable plants.

The water-miscible concentrates are prepared by dissolving from 15% to95% of the compound in 85% to 5% of a water-miscible solvent, such aswater itself or another polar water-miscible solvent, such as2-methoxyethanol, methanol, propylene glycol, diethylene glycol,diethylene glycol monoethyl ether, formamide, and dimethylformamide.Application of the material is made by adding a predetermined quantityof the water-miscible concentrate to a spray tank and applying themixture as such or in combination with a suitable diluent, such as afurther quantity of water or one of the above polar solvents.

The performance of the product in all of the above formulations, whichare applied as liquid sprays, is unexpectedly improved by adding asurfactant or blend of surfactants. Conventional anionic, cationic andnonionic surfactants may be employed.

Illustrative nonionic surfactants are: alkyl polyoxyethylene ethers,polyoxethylene sorbitan monolaurate, polyoxyethylene sorbitan monoleate,alkylarylpolyglycol ethers, alkyl phenol ethoxylates, trimethyl nonylpolyethylene glycol ethers, alkyl phenol ethylene oxide condensates,octyl phenoxy polyethoxy ethanols, nonylphenyl polyethylene glycolethers, condensates of polyoxy ethylenes, polyoxypropylenes, aliphaticpolyethers, aliphatic polyesters, alkylaryl polyoxyethylene glycols, andthe like.

Exemplary anionic surfactants include sodium dodecylbenzene sulfonateand the dioctyl ester of sodium sulfosuccinic acid.

Suitable cationic surfactants include dicoco dimethylammonium chloride,stearamidopropyl dimethyl betahydroxyethylammonium nitrate and the like.

These surfactants are preferably added to the spray tank at the rate of0.1% to 5% by volume to provide good wetting of the spray solution onplant foliage.

Herbicidal concentrates containing surfactants are preferably formulatedas aqueous sprays containing approximately 30% by weight of theappropriate salt, from about 25% to 50% by weight of water and theremainder of said formulation (25%-45% weight) of a selected surfactant.Surfactants which are especially useful in preparing suitable surfactantcontaining concentrates include an octylphenol ethylene oxidecondensate, an ethanolic solution of an alkylphenol ethoxylate, apolyglycolic ether condensate produced from ethylene oxide and an alkylphenol, and an alkyl aryl polyglycolic ether.

Dusts are generally prepared by grinding together about 1% to 25% byweight of the active agent with from about 99% to 75% by weight of asolid diluent such as kaolin, attapulgite, talc, pumice, diatomaceousearth, fullers earth (calcium montmorillonite), wood flour, or the like.

Dust concentrates are prepared in similar fashion excepting that about25% to 95% by weight of the active agent is ground with about 75% to 5%by weight of the diluent.

Dusts and dust concentrates are similarly prepared using from about 5percent to about 95 percent of active ingredient and from about 95 toabout 5 percent of finely divided inert ingredients. These dusts aregenerally applied as such, or they may be further diluted with finelyground inert solids and then applied with conventional dustingapparatus.

Emulsifiable concentrates may be prepared by dissolving or dispersingthe active ingredient and organic solvent, with or without emulsifyingagents, surfactants or the like. Such formulations are then diluted witheither water or an appropriate organic diluent prior to application.

For application of the compounds useful in the process of this inventionto the foliage of the undesirable plant species, the compounds aregenerally formulated as postemergence herbicidal compositions byadmixing a herbicidal adjuvant with a herbicidally effective amount ofthe compound. Suitable adjuvants include one or more conventionallysolid or liquid carriers, diluents and formulation aids, particularlysurfactants.

EXAMPLE I Bioassay of Potential Herbicides--Primary Screen

7.5×7.6×6 cm units are filled with steam-sterilized soil and held ingreenhouse flats (43×43×5 cm). The depth of planting and number of seedsper unit varies with each species.

Weeds tested include:

    ______________________________________                                                              Abbreviation                                            ______________________________________                                        a.  Barnyard grass (Echinochloa crusgalli)                                                                BYGRASS                                           b.  Green foxtail (Setaria viridis)                                                                       FOXTAIL                                           c.  Wild oats (Avena fatua) WILDOAT                                           d.  Nightshade (Solanum sp.)                                                                              NSHADE                                            e.  Velvetleaf (Abutilon theophrasti)                                                                     VLEAF                                             f.  Annual morningglory (Ipomoea purpurea)                                                                MGLORY                                            g.  Yellow nutsedge (Cyperus esculentus)                                                                  YNUTSED                                           h.  Pigweed (Amaranthus retroflexus)                                                                      PWEED                                             i.  Downy brome (Bromus teotorum)                                                                         DBROME                                            ______________________________________                                    

Rationale for selection of these species include:

a. Affected plants are indicators of symptomology of herbicides.

b. One or more species is sensitive to all United States commercialherbicides at the 4 pounds per acre rate.

c. Each species represents a different genus.

d. Economic importance.

e. Will germinate within 7 days and grow very well every month of theyear.

f. Available source of viable seeds.

Germination tests are routinely conducted on new shipments of weeds toestablish a baseline viability.

Preemergence test: Seeds are planted in a sandy loam soil mixture (3parts sandy loam soil to 1 part perlite). Weed seeds are planted at thefollowing densities using a volumetric measurement.

    ______________________________________                                        Weed Species     No. Seeds/Pot                                                ______________________________________                                        Barnyardgrass    50                                                           Green foxtail    45                                                           Wild oats        55                                                           Nightshade       35                                                           Velvet leaf      20                                                           Annual Morningglory                                                                            10                                                           Yellow nutsedge  10                                                           Pigweed          35                                                           Downy brome      50                                                           ______________________________________                                    

Postemergence test: Seeds are planted as described above exceptsupersoil (fir bark, redwood, Canadian peat, and sand) is used. Plantsare fertilized weekly with a 10:10:10 fertilizer mix.

Seedlings are thinned to the following densities:

    ______________________________________                                        Weed Species     No. Seeds/Pot                                                ______________________________________                                        Barnyardgrass    40                                                           Green foxtail    40                                                           Wild oats        40                                                           Nightshade       20                                                           Velvet leaf      20                                                           Annual Morningglory                                                                             5                                                           Yellow nutsedge   5                                                           Pigweed          10                                                           Downy brome       4                                                           ______________________________________                                    

The preemergence test consists of spraying the soil surface with thetest compound at 4 pounds active ingredient (ai) per acre using a beltsprayer equipped with an overhead nozzle. A mixture of an octylphenoxypolyethoxy ethanol surface active agent, a polyoxyethylene sorbitanmonolaurate surface active agent, and a sorbitan monolaurate surfaceactive agent is added at 1000 ppm to increase spreadability of thecompound. The compound is applied at 100 gallons per acre and 21.9 gramsper square inch, and the belt speed is 0.5 miles per hour. Spraying isdone within 6 hrs. after planting. The soil is watered shortly aftertreatment and receives daily watering of a fine mist. Little or nodrainage of water out of the cup bottoms occur.

Postemergence tests involve spraying of established seedlings using thesame equipment and formulation as noted above. Weeds used inpostemergence studies are held in moist soil without additional wateringfor 48 hrs. and then receive daily watering of a fine mist spray.

A test consists of

a. Control--seed only

b. Test--seed plus compound

c. Standard

One replicate of each test is conducted. The level of control isperiodically evaluated with a written evaluation at one and two weeksposttreatment.

The percentage preemergence weed control is assessed using a ranking of0 to 4,

    ______________________________________                                        Ranking                                                                       ______________________________________                                        0          Near 100% germination, no phytotoxicity                                       observed.                                                          1          Near 75% seed germination, no                                                 phytotoxicity to seedlings.                                        2          Seed germination delayed, over 50% seed                                       germination, and/or some phytotoxicity.                            3          Less than 50% seed germination and/or                                         extensive phytotoxicity to established                                        plants.                                                            4          No observed germination and/or                                                establishment.                                                     ______________________________________                                    

Post emergence evaluation:

    ______________________________________                                        Ranking                                                                       ______________________________________                                        0          No chlorosis, suppression or inhibition                                       of plant growth, etc. observed.                                    1          Minimal phytotoxicity, plants generally                                       healthy.                                                           2          Less than 50% plant injury, recovery                                          evident.                                                           3          Over 50% plant injury, some plant death.                           4          All plants dead with no recovery.                                  ______________________________________                                    

The test results are reported in Tables I and II.

                                      TABLE I                                     __________________________________________________________________________    Primary Results: Preemergence Herbicide Screen                                __________________________________________________________________________     Compound R                                                                           ##STR18##                                                                               G*BYGRASS                                                                            E*BYGRASS                                                                           GFOXTAIL                                                                             EFOXTAIL                                                                            GWILDOAT                                                                             EWILDOAT                                                                            GNSHADE              __________________________________________________________________________           Part A                                                                        atrazine 4 lbs/acre                                                                     0      2     0      0     0      3     0                            simazine 2 lbs/acre                                                                     0      4     0      3     0      3     0                     1      OH        2      2     2      2     2      2     1                            Part B                                                                 2      OC.sub.2 H.sub.5                                                                        2      2     2      3     1      3     0                     3      On-C.sub.5 H.sub.11                                                                     2      3     2      3     2      3     0                     4      NH.sub.2  2      3     2      4     1      3     0                     5      NHCH.sub.3                                                                              0      0     1      2     0      0     0                     6      N(CH.sub.3).sub.2                                                                       2      3     2      4     1      3     0                     7      NHn-C.sub.4 H.sub.9                                                                     0      0     0      0     0      0     0                            atrazine 4 lbs/acre                                                                     0      0     0      0     0      2     0                            simazine 4 lbs/acre                                                                     0      0     0      4     0      3     0                     __________________________________________________________________________     Compound R                                                                           ##STR19##                                                                               ENHSADE                                                                              GV LEAF                                                                            EV LEAF                                                                             GMGLORY                                                                             EMGLORY                                                                              GYNUTSED                                                                             EYNUTSED              __________________________________________________________________________           Part A                                                                        atrazine 4 lbs/acre                                                                     4      0    4     0     4      0      0                             simazine 2 lbs/acre                                                                     4      0    4     0     3      0      0                      1      OH        1      1    1     2     2      0      0                             Part B                                                                 2      OC.sub.2 H.sub.5                                                                        0      0    0     1     3      #      #                      3      On-C.sub.5 H.sub.11                                                                     0      0    0     1     3      0      0                      4      NH.sub.2  0      0    0     1     3      0      0                      5      NHCH.sub.3                                                                              0      0    0     0     0      0      0                      6      N(CH.sub.3).sub.2                                                                       0      0    0     0     0      0      0                      7      NHn-C.sub.4 H.sub.9                                                                     0      0    0     0     0      0      0                             atrazine 4 lbs/acre                                                                     0      0    0     0     3      0      0                             simazine 4 lbs/acre                                                                     3      0    0     0     4      0      0                      __________________________________________________________________________                       Compound R                                                                           ##STR20##                                                                               GPWEED                                                                             EPWEED                                                                             GD BROME                                                                            ED BROME                                                                            TOTAL**             __________________________________________________________________________                             Part A                                                                        atrazine 4 lbs/acre                                                                     3    4    0     4     25                                            simazine 2 lbs/acre                                                                     0    2    0     4     27                                     1      OH        0    0    2     3     13                                            Part B                                                                 2      OC.sub.2 H.sub.5                                                                        1    2    1     3     16                                     3      On-C.sub.5 H.sub.11                                                                     0    2    2     3     17                                     4      NH.sub.2  #    #    2     3     16                                     5      NHCH.sub.3                                                                              0    0    0     1     3                                      6      N(CH.sub.3).sub.2                                                                       0    0    0     0     10                                     7      NHn-C.sub.4 H.sub.9                                                                     0    4    1     0     4                                             atrazine 4 lbs/acre                                                                     0    4    0     2     11                                            simazine 4 lbs/acre                                                                     0    4    0     3     21                   __________________________________________________________________________     *G  Germinate;                                                                E = Emergence                                                                 **The totals are of the "emergence" data only, which is more meaningful       # No germination                                                         

                                      TABLE II                                    __________________________________________________________________________    Primary Results: Postemergence Herbicide Screen                               __________________________________________________________________________     Compound R                                                                           ##STR21##                                                                               1BYGRASS                                                                             2*BYGRASS                                                                           1FOXTAIL                                                                             2FOXTAIL                                                                            1WILDOAT                                                                             2WILDOAT                                                                            1NSHADE              __________________________________________________________________________           Part A                                                                        atrazine 4 lbs/acre                                                                     2      1     1      1     2      2     3                            simazine 2 lbs/acre                                                                     2      1     2      2     2      2     3                     1      OH        2      2     2      2     2      1     2                            Part B                                                                 2      OC.sub.2 H.sub.5                                                                        1      3     2      3     2      3     1                     3      On-C.sub.5 H.sub.11                                                                     2      3     2      3     2      3     2                     4      NH.sub.2  0      0     0      0     0      0     1                     5      NHCH.sub.3                                                                              0      0     1      1     1      1     0                     6      N(CH.sub.3).sub.2                                                                       0      0     0      0     0      0     1                     7      NHn-C.sub.4 H.sub.9                                                                     1      1     1      3     1      1     0                            atrazine 4 lbs/acre                                                                     1      3     1      3     1      2     1                            simazine 2 lbs/acre                                                                     1      4     1      3     1      2     2                     __________________________________________________________________________     Compound R                                                                           ##STR22##                                                                               2NHSADE                                                                              1V LEAF                                                                            2V LEAF                                                                             1MGLORY                                                                             2MGLORY                                                                              1YNUTSED                                                                             2YNUTSED              __________________________________________________________________________           Part A                                                                        atrazine 4 lbs/acre                                                                     4      3    3     3     4      1      1                             simazine 2 lbs/acre                                                                     3      1    1     2     3      0      0                      1      OH        2      2    1     2     2      2      2                             Part B                                                                 2      OC.sub.2 H.sub.5                                                                        1      1    1     1     1      1      2                      3      On-C.sub.5 H.sub. 11                                                                    3      2    2     2     3      1      2                      4      NH.sub.2  1      0    0     0     1      0      0                      5      NHCH.sub.3                                                                              0      0    0     0     1      0      0                      6      N(CH.sub.3).sub.2                                                                       1      0    0     0     0      0      0                      7      NHn-C.sub.4 H.sub.9                                                                     0      0    0     0     0      0      0                             atrazine 4 lbs/acre                                                                     4      1    4     3     3      0      1                             simazine 2 lbs/acre                                                                     4      1    4     2     3      0      1                      __________________________________________________________________________                       Compound R                                                                           ##STR23##                                                                               1PWEED                                                                             2PWEED                                                                             1D BROME                                                                            2D BROME                                                                            TOTAL***            __________________________________________________________________________                             Part A                                                                        atrazine 4 lbs/acre                                                                     3    4    2     3     23                                            simazine 2 lbs/acre                                                                     3    4    3     3     19                                     1      OH        2    2    3     3     17                                            Part B                                                                 2      OC.sub.2 H.sub.5                                                                        1    3    2     3     20                                     3      On-C.sub.5 H.sub.11                                                                     2    3    3     3     25                                     4      NH.sub.2  0    0    1     1     3                                      5      NHCH.sub.3                                                                              0    0    1     1     4                                      6      N(CH.sub.3).sub.2                                                                       0    0    0     1     2                                      7      NHn-C.sub.4 H.sub.9                                                                     0    1    2     2     8                                             atrazine 4 lbs/acre                                                                     3    4    1     4     28                                            simazine 2 lbs/acre                                                                     1    4    0     3     28                   __________________________________________________________________________     1 = 1st week;                                                                 2 = 2nd week emergence                                                        **The totals are of the 2nd week data only, which is more meaningful     

EXAMPLE II Preparation of N-n-Butylthioparaconic Acid Amide

A mixture of thioparaconic acid (2.19 g, 15.0 mmol), oxalyl chloride(2.0 mL, 23 mmol) and dimethylformamide (3 drops) in dichloromethane (50mL) was stirred at ambient temperature until gas evolution substantiallyshowed. An additional portion of oxalyl chloride was added (0.4 mL, 5mmol), and when gas evolution again ceased, the mixture was concentratedin vacuo. Twice, portions of cyclohexane (50 mL) were added andsimilarly evaporated. The residue was dissolved in tetrahydrofuran (50mL), the solution chilled, and n-butylamine (3.0 mL, 30 mmol) added. Themixture was stirred thirty minutes. It was then poured into water. Ethylacetate extractive workup gave a crude solid. Recrystallization fromt-butyl methyl ether afforded N-butylthioparaconic acid amide as a creamsolid (1.19 g, 39.4%), mp 63°-64° C. Structural assignment was basedupon ¹ H NMR spectroscopic analysis.

Other, thioparaconic acid amides were prepared in a similar manner.Structural assignments were based upon ¹ H NMR spectroscopic analysis.The resulting thioparaconic acid amides are shown in Table III.

EXAMPLE III Preparation of Ethyl Thioparaconate

A mixture of thioparaconic acid (14.6 g, 0.100 mmol) ethanol (25 mils),benzene (100 mL) and concentrated sulfuric acid (2 mL) was heated atreflux overnight in apparatus having a water trap to allow removal ofwater. The mixture was then concentrated in vacuo. The residue wasdistilled bulb-to-bulb at 0.1 torr, 120° C. to provide ethylthioparaconate as a colorless oil (15.3 g, 87.9%). The ¹ H NMR spectrumwas consistent with the assigned structure.

EXAMPLE IV Preparation of n-Pentyl Thioparaconic Acid

In a similar fashion, n-pentyl thioparaconate was prepared and purifiedby distillation, bulb-to-bulb at 0.1 torr, 130° C. The ¹ H NMR spectrumwas consistent with the assigned structure.

                  TABLE III                                                       ______________________________________                                        Thioparaconic Acid Amides                                                      ##STR24##                                                                                       Recrystallization                                                                            Melting                                     Example  X         Solvent        Point °C.                            ______________________________________                                         V       NH.sub.2  Ethanol        151-152                                     VI       NHCH.sub.3                                                                              n-Butyl methyl ether                                                                         94-95                                       VII      N(CH.sub.3).sub.2                                                                       Toluene        67-69                                       ______________________________________                                    

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

What is claimed is:
 1. A compound having the structure: ##STR25##wherein R¹ is carboxy cyano, ester ##STR26## or amido ##STR27## whereinR² is a straight-chained alkyl group or a branched-chain alkyl grouphaving 1 to 8 carbon atoms, andR³ and R⁴ independently of one anotherrepresent hydrogen, an alkyl having 1 to 8 carbon atoms, a cycloalkylhaving 5 to 6 carbon atoms, or a heterocyclyl having 5 to 6 carbon andhetero atoms, with said hetero atoms selected from sulfur, nitrogen, andoxygen, or, R³ and R⁴ taken together with the nitrogen atom of saidamido group represent pyrrolidinyl, piperidinyl, or piperazinyl.
 2. Thecompound according to claim 1 wherein R² is ethyl or pentyl.
 3. Thecompound according to claim 1 wherein R³ and R⁴ independently of oneanother represent hydrogen, methyl, ethyl, propyl or butyl.
 4. Thecompound according to claim 1 wherein R³ and R⁴ independently of oneanother represent hydrogen or methyl.
 5. A method of controlling plantgrowth comprising applying to the plants or to a habitat thereof aherbicidally effective amount of a compound having the structure:##STR28## wherein R¹ is carboxy, cyano, ester ##STR29## or amido##STR30## wherein R² is of straight-chained alkyl group or abranched-chain alkyl group having 1 to 8 carbon atoms,R³ and R⁴independently of one another represent hydrogen, an alkyl having 1 to 8carbon atoms, a cycloalkyl having 5 to 6 carbon atoms, or a heterocyclylhaving 5 to 6 carbon and hetero atoms, with said hetero atoms selectedfrom sulfur, nitrogen, and oxygen, or R³ and R⁴ taken together with thenitrogen atoms of said amido group represent pyrrolidinyl, piperidinyl,or piperazinyl.
 6. A method according to claim 5 wherein R² is ethyl orpentyl.
 7. A method according to claim 5 wherein R³ and R⁴ independentlyof one another represent hydrogen, methyl, ethyl, propyl or butyl.
 8. Amethod according to claim 5 wherein R³ and R⁴ independently of oneanother represent hydrogen or methyl.
 9. A herbicidal composition whichcontains a carrier, and, as an active ingredient, an effective amount ofthe compound according to claim 1.